opencv利用鼠标获取图像的像素值

void mouseHandler(int event, int x,int y ,int flags,void *p)
{
IplImage *img0, *img1;
img0=(IplImage*)p;
img1=cvCloneImage(img0);
CvFont font;
uchar *ptr;
char label[20];
cvInitFont (&font,CV_FONT_HERSHEY_PLAIN,0.8,0.8,0,1,8);
if(event==CV_EVENT_LBUTTONDOWN)
{
ptr=cvPtr2D(img1, y,x,NULL);
sprintf(label, "(%d, %d, %d)",ptr[0], ptr[1], ptr[2]);
cvRectangle(img1, cvPoint(x,y-12),cvPoint(x+100, y+4),
CV_RGB(255,0,0),CV_FILLED, 8,0);
cvPutText(img1,label,cvPoint(x,y),&font,CV_RGB(255,255,255) );
cvShowImage("src",img1);
}
}

int main()
{
IplImage *src;
src=cvLoadImage("e://kankan//fish.jpg");
assert(src);
cvNamedWindow("src", 1);
cvSetMouseCallback("src", mouseHandler, (void*)src);
mouseHandler(0,0,0,0,src);
cvShowImage("src",src);
cvWaitKey(0);
return 0;

}